This Arabidopsis Research Roundup has five papers that includes two from the John Innes Centre and two from the University of Edinburgh. Firstly Kristen Bomblies’s group at the JIC have investigated the relationship between temperature and meiotic recombination rates. Secondly Veronica Grieneisen and Stan Maree have developed a mathematical model to characterise cell morphologies taken from a 2D image. Andrew Miller from Edinburgh is a co-corresponding author on a study that shows how the Arabidopsis proteome changes in different photoperiods. In the fourth paper Peter Doerner is a co-author on work that looks at the phosphate starvation response. Finally researchers from Bristol and Nottingham contribute to an investigation into a novel genetic component that controls auxin-induced root hair development.

Kristen Bomblies (John Innes Centre) leads this study that investigates the influence of temperature on meiotic recombination rate. They show that in Arabidopsis the number of crossovers positively correlates with increasing temperature. However the mechanistic explanation for the increase at higher temperatures remains opaque as, in contrast to findings from other plants, synaptonemal complex length negatively correlates with temperature.

Veronica Grieneisen and Stan Maree (John Innes Centre) lead this study that has developed the Lobe Contribution Elliptical Fourier Analysis (LOCO-EFA) method. This generates meaningful descriptors from a 2D image of cells that can then be linked to morphological features. This tool allows for the efficient phenotyping of cell morphologies that they demonstrate by analysing images of Arabidopsis leaf pavement cells. They extend this analysis to larger populations where they used LOCO-EFA to predict how cell shapes change when they move into a more crowded space.

Andrew Miller (University of Edinburgh) is the corresponding author on this collaboration with German and Swiss colleagues that compares the Arabidopsis proteome across four photoperiods. They shows coordinated changes across the proteome, most notably at longer photoperiods in the abundance of proteins involved in photosynthesis and metabolism. They show higher translation rates during the day that correspond with the increased RNA abundance that is a characteristic of circadian rhythms. This ‘translational coincidence’ describes the alignment of higher translation rates with high transcript levels and they assigned a mathematical model in an attempt to explain this phenomenon.

Peter Doerner (University of Edinburgh) is a co-author on this global study that characterises the phosphate starvation-mediated induction of the HAD-type phosphatases PPsPase1 (AT1G73010) and PECP1 (AT1G17710). They show that expression of these genes closely follows phosphate status but that their activity does not alter phospate content. The role of these proteins is to control phosphocholine and phosphoethanolamine content, which is a output of changing phosphate conditions. The authors conclude that expression of these genes can be an excellent molecular marker for the phosphate starvation response.

This Belgian-led study includes contributions from Claire Greirson’s and Malcolm Bennett’s labs in Bristol and Nottingham respectively. They investigate the role of the ERULUS (ERU) protein, an auxin-induced receptor-like kinase, during the development of root hairs. ERU localises to the apical root hair plasma membrane and regulates cell wall composition by altering pectin dynamic. The authors conclude that ERU is a key regulator of auxin-mediated control of root hair development.

The first two papers in this weeks Arabidopsis Research Roundup investigate different aspects of the plants response to temperature fluctuations. Firstly Lars Ostergaard (JIC) looks at the influence of temperature in the control of fruit dehiscence whilst Phil Wigge (SLCU) investigates crosstalk between chloroplast and nuclear signaling.

The third paper from Ian Henderson (University of Cambridge) studies the genetic elements that control rates of meiotic recombination. The next paper from the University of Leeds looks at the potential of using MET1 in the induction of novel epi-alleles whilst the penultimate paper includes the GARNet PI Jim Murray (Cardiff University) as a co-author and defines the role of CYCD7;1 in guard cell formation.

The final paper focusses on an enzyme involved in chlorophyll biosynthesis and includes Guy Hanke (QMUL) as a co-author.

Lars Ostergaard (John Innes Centre) is the corresponding author that continues his groups work on the function of the INDEHISCENT protein, on this occasion looking at its involvement in the link between temperature and fruit dehiscence. They show that fruit valve margin development is accelerated at higher temperatures, facilitated by the activity of IND. This activity is associated with the changes in the induction dynamics of the known thermosensory histone H2A.Z and demonstrate a molecular framework for the response to changing temperature during fruit ripening.

Phil Wigge (SLCU) is the corresponding author on this study of the link between light-induced chloroplast signaling and thermotolerance. A forward genetic screen allowed the authors to identify two genes that demonstrated a key role for chloroplast signaling in controlling the activity of heat shock factors (HSFs), which enable the plant to cope with temperature variations. Subsequently they show that altering the binding activities of the HSFA1a protein can mimic heat shock response independent of any changes in temperature.

Ian Henderson (University of Cambridge) is the corresponding author on this collaboration with French colleagues in a study that investigates the factors that control recombination frequency in meiosis. During normal meiotic recombination the majority of double stranded breaks will not form crossovers (over 90%) so to increase this frequency they altered the active dosage of genetic elements that are either pro-crossover or anti-crossover control. This strategy results in a massive increase in crossovers and provides a genetic framework for increasing recombination, a strategy that can be critically important for increasing variation during crop breeding.

This study from the University of Leeds is led by Peter Meyer and investigates how overexpression of the METHYLTRANSFERASE1 (MET1) gene might generate novel epi-alleles that result in altered gene expression. This strategy indeed generated novel epi-alleles that increased expression at loci encoding TEs, non-coding RNAs and protein coding genes. Importantly any altered expression can be transmitted to the next generation, independent of the presence of a MET1 expressing transgene. However the long term stability of these epi-alleles differs in an loci-specific manner.

GARNet PI Jim Murray and Walter DeWitte (Cardiff University) are co-authors on this US-led study that adds complexity to our understanding of the molecular players that control guard cell specification. The authors show that the D-type cyclin CYCD7;1 is expressed during a short time window prior to the symmetry division that forms two guard cells. This activity is controlled by cell-type specific transcription factors acting in the appropriate time period.

Guy Hanke (QMUL) is a co-author on this German-led study that investigates an enzyme reactions that occur during chlorophyll biosynthesis. Specifically they showed that plants lacking the LCAA/YCF54 subunit of the enzyme MgProto monomethylester (MgProtoME) cyclase causes accumulation of MgProtoME and destabilization of the entire cyclase enzyme. This disrupts chlorophyll synthesis and negatively effects photosynthetic activity.

This edition of the Arabidopsis Research roundup beings with a study from SLCU that provides a molecular context to the changes that occur at graft junctions. Second is a study from Edinburgh that reports on the findings of a citizen science plant phenotyping project. Third are two studies from the John Innes Centre that follow-on from previous studies. These characterise the molecular response to seasonal transitions and the factors that control floral development.

The fifth paper is led by Chris Hawes at Oxford Brookes and characterises a novel sub-group of ER localized reticulon proteins. The next paper from the University of Sheffield looks at the whole plant response to changing global carbon dioxide concentrations. The seventh paper from Bristol and York also broadly looks at CO2 but this time at the molecular factors that control stomatal closure in response to both ABA and CO2 signals. Christine Foyer (Leeds) is a co-author on the penultimate paper that characterises the role of ascorbic acid in hormone signaling whilst the final paper from Julian Hibberd at the University of Cambridge analyses a regulatory element that contributes to the evolutionary transition to C4 photosynthesis.

Melnyk CW, Gabel A, Hardcastle TJ, Robinson S, Miyashima S, Grosse I, Meyerowitz EM (2018) Transcriptome dynamics at Arabidopsis graft junctions reveal an intertissue recognition mechanism that activates vascular regeneration. Proc Natl Acad Sci U S A. doi: 10.1073/pnas.1718263115Open AccessThis research was led by Charles Melynk during this time working with Elliot Meyerowitz at SLCU. Grafting is an important classic and contemporary technique in plant biology and this study investigates the gene expression changes that occur on either side of a graft junction. They show asymmetry changes in gene expression on either side of a graft that include an increase in vascular initiation but only in grafted tissues and not in those that are cut and then separated. This study provides an exciting insight into the molecular changes that occur during tissue grafting.

This UK, German and Italian study is led by Sotirios Tsaftaris at the University of Edinburgh and reports on a fascinating citizen science study that evaluated the ability of experts and non-experts to use plant phenotyping software. They demonstrate that non-experts can be effectively involved in plant phenotyping annotation tasks given enough statistical power and if the study is suitably designed.

Hepworth J, Antoniou-Kourounioti RL, Bloomer RH, Selga C, Berggren K, Cox D, Collier Harris BR, Irwin JA, Holm S, Säll T,Howard M, Dean C (2018) Absence of warmth permits epigenetic memory of winter in Arabidopsis. Nat Commun. doi: 10.1038/s41467-018-03065-7Open Access
Caroline Dean and Martin Howard (John Innes Centre) lead this study that further characterise the relationship between the VERNALIZATION INSENSITIVE3 (VIN3) an FLOWERING LOCUS C (FLC) genes in two separate thermosensory processes that monitor long term temperature changes. They suggest that the regulatory strategies currently employed by plants might become less effective as the climate becomes more variable and will have a knock-on effect on plant growth and productivity.

Simonini S, Stephenson P, Østergaard L (2018) A molecular framework controlling style morphology in Brassicaceae. Development. doi: 10.1242/dev.158105Open AccessLars Ostergaard (John Innes Centre) leads this study that characterises how the activity of five transcription factors (TF) integrate with auxin signaling in the control of gynoecium development. The auxin response factor ETTIN is a central controller of this relationship across members of the Brassicaceae and that variation in an ETTIN sub-domain effects TF affinities, interaction strength and gynoecium morphology

This study is led by Chris Hawes (Oxford Brookes) and continues his labs work on the plant ER. They are working on a subgroup of reticulons, which are ER membrane proteins, that have an extended N-terminal domain. Three members of this subgroup show different localisation patterns that indicates that along their sequences are similar they might play different cellular roles.

Williams A, Pétriacq P, Schwarzenbacher RE, Beerling DJ, Ton J (2018) Mechanisms of glacial-to-future atmospheric CO2 effects on plant immunity. New Phytol. doi: 10.1111/nph.15018 Open AccessThis article from the University of Sheffield uses Arabidopsis to investigate the impact that changing climatic CO2 concentrations might have on plant immunity. The authors performed a global analysis on the response to sub-ambient and elevated CO2 and found that both changes causes alterations to salicyclic acid or jasmonic acid response pathways. However these responses are not always opposite, revealing new insights in the response to changing CO2 concentrations.

This is collaborative work between the Universities of York and Bristol and analyses factors that control stomatal closure. They show the TPK1 vacuolar K+ channel is important for ABA and CO2 mediated closure and that the function of this protein is regulated by the KIN7 receptor-like kinase. These activities result in potassium release from the vacuole leading to osmotic changes that contribute to stomatal closure.

Christine Foyer (University of Leeds) is a co-author on this research showing that a defect in ascorbic acid production leads to elevated levels of the hormone ethylene as well as having a wider impact on the control of growth-mediating hormone signalling. This result indicates that the cellular redox buffer AA is a significant contributor to hormone signalling pathways.

Julian Hibberd (University of Cambridge) is the corresponding author on this study that is part of his labs overarching aim of discovering what is necessary to transfer C4 photosynthesis into C3 plants. As part of this work they are searching for master regulator sequences that have allowed for the multiple independent evolution of C4 photosynthesis. They have identified a regulatory duon that is a pair of cis-elements located in coding sequences of genes preferentially expressed in bundle sheath cells of C4 leaves and are also present in C3 plants and algae. Therefore they discuss how C4 plants have co-opted these regulatory elements and how it might be exploited in future molecular engineering projects.

This weeks Arabidopsis Research Roundup begins with a study from SLCU that investigates the interaction between nitrate and cytokinin signaling in the shoot meristem. Next is research from Sheffield that studies changes to the macromolecular composition of the photosynthetic apparatus following the transition from dark to light. Third are three papers that include University of Edinburgh faculty members as co-authors; Gary Loake is involved in a global study on NO signaling, Karen Halliday is included on a study into the relationship between clock components and the PIF-mediated hypocotyl elongation and Naomi Nakayama contributes to the development of a model that explains PIN protein localisation. Cyril Zipfel (TSL) is a co-author on the fifth paper, which introduces a new signaling component in the defence response and whilst the penultimate paper includes Denis Murphy (University of South Wales) and investigates the effect of dioxins on seed development. The final paper documents research from Manchester and Nottingham that uses a cress endosperm as a model to test the elastic properties of thin biological membranes.

Henrik Jonsson and James Locke (SLCU) are corresponding authors on this investigation into the relationship between nitrate and cytokinin signalling in the Arabidopsis shoot meristem (SAM). They show that nitrate availability determines the size of the SAM, which is controlled by the transport of cytokinin precursors from the root to the shoot. A discussion about this paper with lead author Benoit Landrien and Professor Jonsson is available on the GARNet YouTube and iTunes channels.

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This research in this manuscript has come from the University of Sheffield with Matthew Johnson as the corresponding author. They have used atomic force microscopy (AFM) to investigate how the transition from dark to light affects the macromolecular architecture of the photosynthetic apparatus within the thylakoid membrane. This transition does not alter the antenna size of either photosystem yet increases the number of thylakoid grana. Overall these changes serve to regulate the balance between light harvesting, CO2 fixation and enabling the protection of PSII activity from the destructive effects of non-photochemical quenching.

Gary Loake (University of Edinburgh) is a contributor to this Korean-led manuscript that has performed expression analysis on plants treated with S-nitrosocysteine (CySNO). They have identified many novel NO-responsive transcription factors and were able to confirm the role of three random TFs in this response following analysis of loss of function mutants. This paper provides new insights into the molecular components that contribute to NO signalling during plant defence and immunity.

Karen Halliday (University of Ediburgh) is a co-author on this Spanish-led study that investigates how the expression of PHYTOCHROME-INTERACTING FACTORS (PIFs) genes is controlled. The activity of PIFs are responsible for determining the rate of hypocotyl elongation in different light conditions and this paper demonstrates that PSEUDO-RESPONSE REGULATORS PRR9/7/5 proteins act antagonistically to the PIFs by interacting at the promotor of the CDF5 transcription factor. This provides a mechanism to explain the circadian-controlled regulation of hypocotyl cell elongation.

Naomi Nakayama (University of Edinburgh) is a co-author on this Mexican-led study that proposes a physico-genetic model that explains the localization of PIN auxin transporter proteins to the Arabidopsis plasma membrane. This model confirms experimental observations and allows the prediction that mechanical forces can predominate over molecular components.

This Chinese-led paper includes Cyril Zipfel (TSL) as a co-author and identifies the U-box proteins PUB25 and PUB26 as E3 ligases for the cytoplasmic kinase BIK1, which is a key rate limiting component of the plant defence response. This multi-protein regulatory module provides another level of complexity to our understanding of the molecular factors involved in plant immunity.

Denis Murphy (University of South Wales) is a co-author on this Syrian-led study that uses Arabidopsis seeds to test the negative effects of dioxins. Seeds treated with dioxins have a wrinked phenotype that corresponds to changes in the expression of genes related to lipid and carbohydrate metabolism. Overall this study reveals a novel set of genetic changes effects caused by dioxins that explain the profound effects on seed development.

Plant scientist Mike Holdsworth (University of Nottingham) is a co-author on this paper that has used the endosperm from garden cress (Lepidium sativum) as the experimental model to define the elastic properties of a thin biological surface. Indentation experiments have been classically used to measure these properties and then develop mathematically models that explain their characteristics. These models rely on an assumed flat surface whereas in reality any surface will often be curved. By obtaining measurements from identations studies on the cress endosperm they are able to better refine the models that explain the properties of the membrane in this context.

This workshop is designed to encourage interactions and discussion about the use of CRISPR-Cas9 gene editing in plant systems.

We are encouraging ECRs to attend the meeting and are providing nine opportunities for talks by people who have submitted abstracts. We are also hosting extended poster sessions.

The workshop has three main plenary sessions that will look at the technical aspects of using GE in different plant species. In addition we are hosting a session with a extended opportunity for debate regarding the policy decisions that surround use of this technology.

The full workshop schedule is here: https://garnet-ge-workshop.weebly.com/schedule.html

The cellular mechanics of auxin perception and signaling have been well studied over the past two decades. The pivotal interaction that controls this activity involves the auxin-dependent contact between the TIR1 receptor and a family of transcriptional regulators called AuxIAA proteins. This interaction has been characterised at a structural level with the auxin indole-3-acetic acid (IAA) shown to act as a ‘molecular glue’, stabilising the interaction between TIR1 and the AuxIAA. This subsequently causes the degradation of the AuxIAA protein, setting off a cascade of auxin-dependent transcriptional responses.

Revealing the precise kinetics of this interaction is complicated by the fact that TIR1 belongs to a family of six related receptors and the AuxIAA family comprises 29 members. Although IAA is able to mediate the interaction between each of these family members, the TIR1 auxin binding pocket is somewhat promiscuous, with a wide range of auxin analogues being able to illicit a similar responses.

In order to develop a synthetic auxin signaling complex that was free from the complexities of varying protein family interactions, Keiko Torii and co-workers from the University of Washington and Nagoya University employed a bump-and-hole strategy. This technique sits at the interface of chemistry, biology and engineering and in this case was able to create a functional synthetic receptor-substrate interaction that did not interfere with the endogenous activity of TIR1-AuxIAA. This research has been published in Nature Chemical Biology.

https://www.nature.com/articles/nchembio.2555

https://www.nature.com/articles/nchembio.2555

Using the bump-and-hole strategy the authors interrogated the TIR1 auxin binding-pocket, predicting that removal of a bulky phenylalanine would result in a ‘hole’ whose space could be filled by a version of IAA that included an aryl-ring ‘bump’.

The authors showed that this ‘concave (ccv) TIR1’ was able to interact with the ‘convex (cvx) IAA’ and remarkably be able to elicit a biological relevant response in vivo. Generation of transgenic plants expressing ccvTIR1 or the application of exogenous cvxIAA has little effect on plant growth. However in the presence of cvxIAA, these ccvTIR1 transgenic plants show alterations in primary root elongation, lateral root development and gene expression changes characteristic of an auxin response. Therefore this paper synthetically replicated the auxin signaling module, whose function absolutely relies upon the presence of both components.

This research is a superb example for the use of modeling and synthetic chemistry to facilitate the study of a complex biological system. There is no doubt that the ccvTIR1-cvxIAA system is an important tool for study of the cellular auxin response as well for the tissue-specific activities of this do-it-all phytohormone. We await the development of an engineered enzyme that can produce cvxIAA in vivo so that the system will not need to rely on any external additions!!!

This Arabidopsis Research Roundup has five papers that includes two from the John Innes Centre and two from the University of Edinburgh. Firstly Kristen Bomblies’s group at the JIC have investigated the relationship between temperature and meiotic recombination rates. Secondly Veronica Grieneisen and Stan Maree have developed a mathematical model to characterise cell morphologies taken[…]

The first two papers in this weeks Arabidopsis Research Roundup investigate different aspects of the plants response to temperature fluctuations. Firstly Lars Ostergaard (JIC) looks at the influence of temperature in the control of fruit dehiscence whilst Phil Wigge (SLCU) investigates crosstalk between chloroplast and nuclear signaling. The third paper from Ian Henderson (University of[…]

Charles Melnyk discusses a new paper published in PNAS that describes the molecular events that occur during grafting. The paper is entitled ‘Transcriptome dynamics at Arabidopsis graft junctions reveal an intertissue recognition mechanism that activates vascular regeneration‘ http://blog.garnetcommunity.org.uk/wp-content/uploads/2018/03/Melynk_180301.mp3Podcast: Play in new window | DownloadSubscribe: iTunes | Android | RSS

This edition of the Arabidopsis Research roundup beings with a study from SLCU that provides a molecular context to the changes that occur at graft junctions. Second is a study from Edinburgh that reports on the findings of a citizen science plant phenotyping project. Third are two studies from the John Innes Centre that follow-on[…]

This weeks Arabidopsis Research Roundup begins with a study from SLCU that investigates the interaction between nitrate and cytokinin signaling in the shoot meristem. Next is research from Sheffield that studies changes to the macromolecular composition of the photosynthetic apparatus following the transition from dark to light. Third are three papers that include University of[…]

GARNet with support from the Bristol Centre for Agricultural Innovation and New Phytologist are organising a Gene Editing Workshop that will take place at the University of Bristol on March 26th-27th 2018. This workshop is designed to encourage interactions and discussion about the use of CRISPR-Cas9 gene editing in plant systems. We are encouraging ECRs[…]

The cellular mechanics of auxin perception and signaling have been well studied over the past two decades. The pivotal interaction that controls this activity involves the auxin-dependent contact between the TIR1 receptor and a family of transcriptional regulators called AuxIAA proteins. This interaction has been characterised at a structural level with the auxin indole-3-acetic acid[…]

This weeks Arabidopsis Research Roundup begins with two papers from Royal Hollaway University of London that investigate the factors that control leaf development in the dark and the control of PIN1 phosphorylation. Third is a paper from Bristol that demonstrates the translation of research from Arabidopsis into coriander with regard the control of the response[…]

Enrique Lopez-Juez (Royal Holloway University of London) introduces a paper from that attempts to answer a critical question in plant science ‘Why do plants makes leaves in the dark‘? http://www.plantphysiol.org/content/early/2017/12/28/pp.17.01730.long http://blog.garnetcommunity.org.uk/wp-content/uploads/2018/01/Lopez_180116.mp3Podcast: Play in new window | DownloadSubscribe: iTunes | Android | RSS